Conventionally, a linear digital modulation method such as π/2 shift binary phase shift keying (BPSK) is known, for example, as a modulation method used in a wireless communication system (for example, refer to Non-Patent Document 1).
In the linear digital modulation method, an envelope of a transmitted band signal fluctuates, so that power consumption during signal amplification increases as compared to that in a non-linear digital modulation method such as minimum shift keying (MSK). However, in the linear digital modulation method, it is known that both narrow band and highly sensitive reception may be satisfied at the same time by using a root-raised cosine filter that satisfies a Nyquist first criterion as a transmission/reception band-limiting filter.